1. Field of the Invention
The present invention relates to a method of manufacturing a droplet jetting head, a droplet jetting head obtained by the method, and a droplet jetting apparatus equipped with the droplet jetting head, and specifically, to a method of manufacturing a droplet jetting head that jets droplets in order to form an image and is suitable for ink jet recording, a droplet jetting head obtained by the method, and a droplet jetting apparatus equipped with the droplet jetting head.
2. Description of the Related Art
A droplet jetting apparatus that jets droplets by an ink jet printing method or the like to form an image on a recording medium by aggregation of dots formed by the droplets is known.
The performance of this kind of droplet jetting apparatus greatly depends on the performance of the droplet jetting head provided in this apparatus. Such a droplet jetting head imparts electrical or thermal energy to a droplet, thereby jetting the droplet from an opening for jetting, the droplet being stored until the droplet is jetted.
A configuration of a general droplet jetting head is shown in FIG. 1. Here, the droplet jetting head 10 is configured such that a substrate 18 that forms a pressure chamber, provided with a pressure chamber 12 holding a liquid and imparting pressure, an opening 14 for jetting a droplet, and an opening 16 for liquid supply that supplies the liquid to the pressure chamber 12, is bonded together with an adhesive 24 to a substrate 22 that forms a flow passage, provided with a liquid passage 20 that supplies the liquid for jetting from a tank (not shown) or the like filled with droplets. The substrate 22 that forms a flow passage includes a relief portion 28 for a pressure supply unit 26 that imparts pressure to the liquid held by the pressure chamber 12, and the pressure supply unit 26 is disposed in this space. Further, a wiring 27 for driving the pressure supply unit 26 is provided.
The substrate 22 that forms a flow passage and the substrate 18 that forms a pressure chamber are firmly bonded together by an adhesive. As the bonding method, an adhesive is applied to the surface of the substrate 18 to form an adhesive layer 24, the substrate 22 is superposed and compressed on the surface of the substrate 18 such that the opening 16 for liquid supply and a through hole (liquid passage) 20 formed in the substrate 22 are substantially aligned with each other, and both substrates are bonded together by curing the adhesive layer 24.
Here, when both of the substrates are pressed and bonded together, a situation may occur in which a part of the adhesive that has not been cured extrudes and protrudes into the through hole and is cured. When a portion of the adhesive protrudes in this way, it affects the flow passage of the liquid. When the liquid includes a solvent or an oil component, such as ink, a part of the resulting cured adhesive may melt and become mixed into the liquid, or a part of the adhesive may be peeled off and become mixed into the liquid due to surface strength degradation thereof, thereby affecting the composition of droplets. Other adverse effects, such as the clogging of a nozzle caused by the peeled-off adhesive, are also a concern.
When the amount of the adhesive is decreased in order to prevent the above adverse effects and the like, the adhesion between the substrates becomes weaker, and the durability of the jetting head deteriorates.
As a technique that can be applied in order to address this issue, a technique whereby a metal or a metal oxide as a bonding layer is provided at least at the joining areas of the substrates to be joined together has been suggested, in order to prevent the peeling off of an adhesive and improve reliability (for example, refer to JP-A No. 2007-245589). However, formation of the bonding layer with a metal or the like causes a problem in that an increase in process steps, such as a film forming step and a patterning step, complicate the process, and furthermore the problem of adhesive protrusion is not completely solved. A further technique, whereby a groove that receives adhesive is formed in a substrate that forms a flow passage, is known as a method of preventing protrusion of adhesive (for example, refer to JP-A No. 7-195693). However, this technique forms a recess, as seen in a joining cross-section, in order to receive excessive adhesive therein, and the step of forming the recess is complicated and therefore problematic.